Process for separating liquids of different specific gravities



Feb. M, 1933. s. A. B. DAHLGREN PROCESS FOR SEPARATING LIQUIDS OF DIFFERENT SPECIFIC GRAVITIES Original Filed June 21, 1930 Patented Feb. 14, 1933 UNITED STATES PATENT OFFICE SVEN ALFRED BERTIL DAHLGREN, OF ALSTEN, SWEDEN, ASSIGNOR TO THE LAVAL SEPARATOR COMPANY, OF NEW YORK, N. Y., A CGRE'ORATION OF NEW JERSEY PROCESS FOR SEPARATING LIQUIDS OF DIFFERENT SPECIFIG GRAVITIES "seal of the heavier liquid in the separating vessel. If the separation takes place in a centrifuge and if a mixture of the two liquids is fed into the bowl of the centrifuge, the heavier liquid will be separated out towards the periphery of the bowl, where it displaces a corresponding quantity of liquid via the liquid seal, said liquid leaving the bowl through an outlet at a certain distance from the axis of rotation of the bowl. The lighter liquid moves inwards towards the centre and is discharged from the bowl at a smaller distance from the axis of rotation of the bowl. To attain the highest separating efficiency, the outlet radius should be such that the level between the lighter and the heavier liquid in the centrifugal bowl is at the greatest possiblediameter. If the liquids contain solid impurities, which must be separated out, the correct determination of said outlet radius is of the greatest importance for the result of the separation as these impurities generally are more difiicult to separate than the liquids and also interfere with the separation of the liquids.

To obtain in every case the most advantageous position of the level in the bowl according to the specific gravities of the liquids, the outlets for liquid have been arranged in such manner that their distance from the 3 axis of rotation of the bowl can be varied.

A common method is to take out one of the liquids through a ring that is concentric with the axis of rotation of the bowl, said ring being replaceable by a similar ring of any desired diiferent inner diameter. Another method is to move the outlet radius of the heavier or the lighter liquid in a radial direction by means of ascrew.

The regulation brought about by exchange of rings or by adjustment of screws involves great inconveniences, especially as the specific gravities of the liquids often vary. It may even happen that the specific gravities of the liquids vary during the separation. This is for instance the case when separat- Application filed June 21, 1930, Serial No. 462,773, and in Sweden July 3, 1929. Renewed July 13, 1932.

ing the press-liquid obtained from olives. Whereas the specific gravity of the olive oil is comparatively constant, the specific gravity of the fruit water may vary between 1.00 and 1.12. At the same time a very exact adjustment of the bowl is of the utmost importance for the result of the separation, making it necessary often to stop theseparator so that the'levels can be regulated. In unfavorable cases such a regulation of the levels may be necessary several times an hour, so that the centrifuge works in an uneconomi-' cal manner and is troublesome to operate.

The object of the present invention is to avoid the necessity of manual regulation of either of the liquid outlets or of stoppage of the centrifuge in order to maintain the conditions required for eiiicient' separation. Specifically the object of the invention is attained by the maintenance of a constant level between the two liquids in the separating chamber independent of the relatives specific gravities of the liquids. The invention also comprises novel structural features in the centrifuge itself, although the process is not dependent for its execution on a centrifuge of any particular construction.

In the drawing: 1

Fig. 1 is a diagram illustrating the prin ciple of the invention by means of a decant-' ing apparatus wherein separation is effected by gravity.

Fig. 2 is a vertical section though a centrifuge embodying my structural improvements and adapted to carry out my improved process.

Fig. 3 is a plan view of the central feed tube,

the initial lighter liquid outflow channel and the upper surface of the plate forming the bottom of the auxiliary separating chamber.

Fig. 4: is a detail sectional view of means for regulating the radius of the outlet from the outflow passage of once-separated lighter liquid. I

In order to illustrate the principle of the invention in a simple manner, it will be assumed that the separation is taking place under the influence of gravity instead of under centrifugal force,'and for this purpose reference will first be made to Fig. 1.

.which extends down to about, but not necessarily exactly,'the levelat which one desires to keep the boundary level between the two liquids in the separating vessel. Through the-tube G the oil is led into a chamber R in which the oil must pass through a layer of water H and finally discharges through the fixed oil outlet I. The oil is clean when it again meets the water in the chamber R and the water has also been liberated from solid impurities, so that the liquids easily eflect a clean separation.

If now the specific gravity of the water suddenly increases, the weight of the column of water D also increases. In order that there shall be equilibrium between said column of water and the column of liquid under the fixed oil outlet I, the height of the column of water H must be such that the pressure of the same plus the pressure of the column of oil over it is equal to the pressure of the column of water D. In order that the oil shall be-able to surmountthe increased pressure of 'the water, it is necessary that the height of the column of oil E shall increase simultaneously. The level between'water and oil in the separating vessel will still be at the same height, water and oil discharge at fixed lev- ,els, and the only result of the variation in the specific gravity of the water is that the height of the column of oil E automatically increases or decreases. I

Figs. 2 and 3 show a centrifugal bowl embodying my improved construction and adapted to carry out my improved process in accordance with the principle shown in Fig.

. '1 and above described. j-The mixture of liquids is fed into the bowl through the central 'feed tube Aand is introduced into the separating chamber B through the channels K andjL. The heavier liquid as well as the solid impurities move towards the wall of the bowl undcrthe influence of the centrifugal force. The v former discharges continuously through the channels M to the fixed outlet C, whereas the heavier solid impurities that are not carried out with theliquid deposit on the wall' of the bowl. The lighter liquid moves in wards to-the centre of the bowl and is graduallyliberated from the heavier liquid and the impurities. The bowl shown in the figure is fittedwith apileof discs, the object of the same being to increase the separating efliciencyof the bowl. The purified oil flows pile of discs in this chamber. The level N in the bowl between the heavier and the lighter liquid keeps at a constant distance from the axis of rotation of the bowl if the specific gravity of either of the liquids should vary, analogous to whatis the case with the static separating tank illustrated in Fig. 1.

By lengthening or shortening the tubes G at their outer ends, it is possible to move the level between the liquids from or towards the centre of the bowl respectively. The level for the discharge of the oil inthe. chamber R and thus also the level between the liquids can be made variable'by means of specialregulating devices, for instance, by means of screws U, provided with a central hole, at

the outer ends of the tubes G as shown in Fig. 4:. a

. In certain cases, as, for instance, when the specific gravities lie close to each other and undergo but small changes during theseparation, it may be desirable to place the outlets for the liquids at as small a diameter as possible, one advantage of this being reduced power consumption for the separation. It is;

also suitable to provide regulating devices for the variation of the diameterof outlets for the liquids, said regulating devices having, however, no influence on the position of the level betweenthe two liquids in the centrifugal bowl.

The separation of oil and water and of olive. oil and fruit water are merely examples of mixed liquids capable of separation by my improved process and centrifuge. It should be clearly understood that the invention is applicable to all mixtures of liquids which are capable of being centrifugally separated.

No claim is made herein tothe novel structural features of the. centrifuge, the same forming the subject-matter of a separate application filed April 28, 1931, Serial No. 533, 98.

Having now fully described my invention, what I claim and desire to protect by Letters Patent is:

1. In the separation of two liquids of different specific gravities in which the separated heavier liquid; that has been separated in the main separating space is discharged.

through a liquid seal formed by the heavier liquid, the process which comprises flowing the lighter liquid that has been separated in themain separatingspace into an auxiliary body of the heavier liquid communicating *ith said liquid seal and at a level approximating the level between the two liquids in the main separating space, and in said auxiliary body of the heavier liquid separating therefrom said lighter liquid and discharging it from an outlet at a level between the outlet for the heavier liquid and the level of the lighter liquid in the main separating space, whereby the level between the two liquids in the main separating space is maintained constant notwithstanding varations in the specific gravities of the two liquids.

2. In the centrifugal separation of two liquids of different specific gravities in which the heavier liquid that has been separated in the main separating space is discharged therefrom through a liquid seal formed by the heavier liquid and thence flows inward toward the axis of rotation and discharges through an outlet at a smaller distance from the axis of rotation than the level between the two liquids in the main separating space, the process which comprises flowing the lighter liquid that has been separated in the main separating space into an auxiliary body of the heavier liquid communicating with said liquid seal and at a level approximating the level between the two liquids in the main separating space, and in said auxiliary body of the heavier liquid again separating the lighter liquid from the heavier liquid and flowing it inward toward the axis of rotation and discharging it through an outlet between the outlet for the heavier liquid and the level of the lighter liquid in the main separating space, whereby the level between the two liquids in the main separating space is maintained constant notwithstanding variations in the specific gravities of the two liquids.

b. In the centrifugal separation of two liquids of different specific gravities in which the heavier liquid that has been separated in the main separating space is discharged therefrom through a liquid seal formed by the heavier liquid and thence flows inward toward the axis of rotation and discharges through an outlet at a smaller distance from the axis of rotation than the level between the two liquids in the main separating space, the process which comprises flowing the lighter liquid that has been separated in the main separating space through an auxiliary body of the heavier liquid communicating with said liquid seal and therein again separating the lighter liquid from the heavier liquid and discharging it.

4. In the centrifugal separation of two liquids of diiierent specific gravities in which the heavier liquid that has been separated in the main separating space is discharged therefrom through a liquid seal formed by the heavier liquid and thence flows inward toward the axis of rotation and discharges through an outlet at a smaller distance from the axis of rotation than the level between the two liquids in the main separating space, the process which comprises flowing the lighter liquid that has been separated in the main separating space through an auxiliary body of the heavier liquid communicating with said liquid seal and therein again separating the lighter liquid from the heavier liquid and discharging it through a fixed outlet at a radial distance from the axis of rotation between the radial distances of the outlet for the heavier liquid and the level of the lighter liquid in the main separating space.

5. In the centrifugal separation of two liquids of different specific gravities, the process which comprises separating the two liquids in a main separating space, discharging therefrom all the separated heavier liquid through a liquid seal of such heavier liquid and discharging all the lighter liquid through another liquid seal of said heavier liquid.

6. In the centrifugal separation of two liquids of different specific gravities, the proce s which comprises separating the two liquids in a main separating space, discharging therefrom all the separated heavier liquid through a liquid seal of such heavier liquid communicating with the peripheral zone of separated heavier liquid and outflowing from the n sin separating space all the lighter lli d into another liquid seal of said heavier liq did at a level approximating the level between the two liquids in the main separating space, and reseparating the lighter liquid f om the heavier liquid of the second liquid seal and discharging it.

7. In the centrifugal separation of two liquids of different specific gravities, the process which comprises separating the two liquids in a main separating space, discharging therefrom all the separated heavier liquid through a liquid seal of such heavier liquid communicating with the peripheral zone of separated heavier liquid and outflowing from the main separating space all the lighter liquid into another liquid seal of said heavier liquid at a level approximating the level between the two liquids in the main separating space, and reseparating the lighter liquid from the heavier liquid of the second liquid seal; and thence flowing the lighter liquid through afixed outlet at a radial distance from the axis of rotation between the radial distances of the heavier liquid outlet and the level of the lighter liquid in the main separating space.

In testimony of which invention, I have hereunto set my hand, at Stockholm, Sweden, on this 2nd day of June, 1980.

SVEN ALFRED BERTlL DAHLGREN. 

